Implantable medical devices (IMD's) are devices placed inside a body to monitor certain physiological signals and provide or permit therapy to an organ or tissue in response to the physiological signals. Examples of IMD's include heart monitors, therapy delivery devices, pacemakers, implantable pulse generators, pacer-cardio-defibrillators, implantable cardio-defibrillators, cardiomyo-stimulators, nerve stimulators, gastric stimulators, brain stimulators, and drug delivery devices.
In the current state of the art, the sensing and/or stimulation functions of the IMD are controlled from an implantable module, typically housing a power source, a communications means that permits control of the module, such as by telemetry, logic circuitry that controls the functioning of the module independent of inputs via telemetry, and electronics for modulating the inputs and outputs to and from the module. The sensing and/or stimulation functions typically are performed by leads, implanted near a site of interest or the “targeted tissue,” that comprise tissue interaction elements, such as stimulation electrodes, drug ports, sensors and sensing electrodes and the like. The tissue interaction elements are in electrical communication with the implantable module via dedicated conductors that extend the distance from the targeted tissue to the implantable module. Typically, each tissue interaction devices is connected to its own dedicated conductor. Each dedicated conductor requires a feedthrough access from the control module, a wire conductor for transmitting electronic signals, means for insulating the wire conductor from the body and from other wire conductors, and means for connecting the wire conductors to the tissue interaction devices. Because the dedicated conductors may extend for relatively long distances, such as, for example, from the abdomen to the spinal cord, the conductors typically are configured to withstand significant tensile and flex demands implied by the long run. The conductors typically also are adapted to minimize energy loss due to impedance. Further, the long conductors should be configured to reduce or eliminate dangerous exposure of the patient to the coupling of energy into the conductors from external alternating magnetic fields in such environments such as magnetic resonance imaging, diathermy, and theft detection. Accordingly, to meet these demands and requirements, the conductors often are sizable.
While it may be advantageous to use ten, twenty, fifty or more tissue interaction devices at a targeted site, the use of this many tissue interaction devices has not been feasible because of the size limitations imposed by the body on the number of sizable conductors that can be implanted, particularly through arterial or venous blood vessels. In addition, the long conductor runs combined with signal-to-noise requirements of certain sensing and/or stimulation systems requires sophisticated design of the leads that house the tissue interaction devices to minimize noise and maximize isolation of the conductors from each other and the surrounding environment.
Accordingly, it is desirable to provide an improved medical system and apparatus for interacting with a tissue of a patient. In addition, it is desirable to provide an improved method for interacting with a tissue of a patient. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.